Don't worry, they say it's a risk worth taking!June 28, 2010 -- The risk of fever-related seizures in infants nearly doubles with the four-in-one measles-mumps-rubella-chickenpox vaccine (MMRV) compared to when the measles-mumps-rubella (MMR) vaccine and chickenpox vaccine are given separately, according to a new study.

Even so, the risk of febrile seizures -- convulsions brought on by fever -- is low with either approach, says researcher Nicola P. Klein, MD, PhD, a research scientist at the Kaiser Permanente Northern California Division of Research and co-director of the Kaiser Permanente Vaccine Study Center, Oakland.

"Overall, the risk for febrile seizures from all measles-containing vaccines is low, less than 1 febrile seizure per 1,000 doses," Klein says. "However, MMRV is associated with a doubling of the risk of febrile seizures among 1-2-year-olds when compared with children who received separate, same-day administration of MMR and V."